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Re: How to find number of processors?

Steve M. Robbins <steve@sumost.ca> (09/01/2010):
> Hello,


>     unsigned thread::hardware_concurrency()
>     {
> #if defined(PTW32_VERSION) || defined(__hpux)
>         return pthread_num_processors_np();
> #elif defined(_GNU_SOURCE)
>         return get_nprocs();
> #elif defined(__APPLE__) || defined(__FreeBSD__)
>         int count;
>         size_t size=sizeof(count);
>         return sysctlbyname("hw.ncpu",&count,&size,NULL,0)?0:count;

> #elif defined(BOOST_HAS_UNISTD_H) && defined(_SC_NPROCESSORS_ONLN)
>         int const count=sysconf(_SC_NPROCESSORS_ONLN);
>         return (count>0)?count:0;

I've just checked that sysconf(…) is available, and I guess it should
do the job. Unfortunately I only have a UP machine to test this on, so
I can't tell for sure.

So at first glance, somebody wanting to provide a patch might just
want to tweak the _GNU_SOURCE check to exclude the __FreeBSD_kernel__
case, so that the BOOST_HAS_UNISTD_H && _SC_NPROCESSORS_ONLN case is


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